Bone defects caused by trauma, disease or congenital deficiency have traditionally been restored with graft procedures using endogenous bone, exogenous bone, or synthetic substitutes, including metals, ceramics, and polymers, as replacement materials. Although these methods have been used successfully for decades, all of them present drawbacks. During the last few years much research has been devoted to the development of bone substitutes that eventually degrade to allow re-growth of the natural bone. These efforts have led to the development of new biomaterials and a better understanding of the bone-forming process. In light of this new knowledge, TDA Research, Inc. (TDA) plans to develop a new inorganic-organic composite that can be used as a bone substitute to repair large and irregular bony defects. TDA's composite bone substitute will be used as a paste or putty at the time of the surgical procedure and can be shaped and processed in vivo. The cured material will have excellent mechanical properties and become porous after implantation. Porosity is crucial for obtaining osteoconductivity. Degradation products from TDA's biodegradable bone substitute will be non-toxic. The composite will be designed to retain strength as the degradation proceeds. PROPOSED COMMERCIAL APPLICATIONS: TDA's bone substitute will be used in the biomaterial industry of hard tissue replacement. Currently the biomaterial industry spends $2.3 billion on bone replacement materials (Suchanek 1998).